Motor-Driven Shift Position Learning Without Current Noise
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Solution Overview
Problem
Existing shift-by-wire systems face challenges in accurately learning shift positions due to noise from electromagnetic waves, affecting the precision of learning the R and N positions, which in turn impacts the accuracy of the P and D positions.
Innovation Solution
A shift device with a motor-driven shift switching member and a positioning member that learns shift positions based on the change in load torque while moving through valley portions, using a detent spring and a driving force transmission mechanism to detect the width of backlash and estimate disturbance torque, allowing for precise positioning without relying on current value noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the shift device learns positions based on current values detected by a current sensor, then the learning process can be implemented, but noise from electromagnetic waves affects the accuracy of detecting valley portions, making it difficult to accurately learn shift positions
Solution Approach 1:
The patent replaces the electrical sensing method (current sensor detecting electromagnetic signals) with a mechanical sensing method (positioning member detecting physical valley portions). The positioning member mechanically engages with the valley portions of the shift switching member, and the controller detects shift positions based on the mechanical position of the positioning member rather than noisy electrical current signals. This substitution eliminates the harmful effect of electromagnetic noise on measurement precision.
2Device complexity
If offset control is used to learn P and D positions from learned R and N positions, then the learning process can be simplified, but inaccurate learning of R and N positions propagates errors to P and D positions
Solution Approach 1:
The positioning member automatically and independently detects each shift position (P, R, N, D) by mechanically engaging with the corresponding valley portions. Each position is detected self-containedly through the mechanical interaction between the positioning member and the valley portions, without relying on offset calculations from other positions. This eliminates error propagation while maintaining learning control functionality.
Data Source
AI summary
A shift device includes: a shift switching member including a plurality of valley portions corresponding to shift positions; a motor that includes a rotor and a stator and that is configured to drive the shift switching member; and a positioning member configured to establish the shift positions in a state in which the positioning member is fitted into any one of the plurality of valley portions of the shift switching member. The shift device is configured to learn the shift positions based on a change amount of a load torque applied to the motor while the positioning member is moved to continuously pass through the plurality of valley portions.